1. Field of the Invention
The present Invention relates to a method for producing ε-caprolactam, and more particularly relates to a method for producing ε-caprolactam by fluidizing a layer of catalyst particles so as to bring a gas containing cyclohexanone oxime into contact with the catalyst particles.
2. Related Art
ε-Caprolactam is useful as a raw material for nylon or the like. Japanese Patent Application Laid-Open No. 2000-229939 discloses a method for producing ε-caprolactam, by using so-called fluidized bed reaction apparatus, in that a raw material gas containing cyclohexanone oxime is supplied to a catalyst layer having solid catalyst particles so as to bring the raw material gas into contact with the catalyst particles, while maintaining the catalyst layer in a fluidized state. A fluidized-bed reaction apparatus is known, such as an apparatus equipped with a porous gas diffusion plate and having a catalyst layer of solid catalyst particles on the plate. The apparatus can be employed so that the raw material gas is supplied to the catalyst layer through a large number of the holes formed in the porous gas diffusion plate, while maintaining the catalyst layer in the fluidized state. The raw material gas is brought into contact with the solid catalyst particles in the catalyst layer, which is in the fluidized state, to provide a reaction gas containing a product (ex., ε-caprolactam). Conventionally, the fluidized-bed reaction apparatus has a porous gas diffusion plate with the average diameter of the holes of 6 mm or larger, or at least 4–5 mm, in order to supply the raw material gas easily and not to plug the holes.
However, the production method using the conventional fluidized-bed reaction apparatus has problems such that conversion of the raw material (ex. cyclohexanone oxime) and selectivity to the product (ex., ε-caprolactam) are insufficient.
With objects of solving the problems, especially when using cyclohexanone oxime as a raw material, the production method of ε-caprolactam has been researched. As a result, inventors of the present invention have found that the size of the holes in the porous gas diffusion plate of the fluidized-bed reaction apparatus is related with the conversion of the raw material, cyclohexanone oxime, and the selectivity to the product, ε-caprolactam. Based on such findings, the present invention has been accomplished.